Electrostatic Self‐Assembly Heterostructured MXenes/ Wasted PET‐Derived Carbon for Superior Capacitive Energy Storage

Abstract Carbon materials have become a focal point in supercapacitors (SCs) due to their perfect charge–discharge behavior, relatively low cost, and excellent electrochemical stability, but the limited electrochemical activity restricts their further development. MXenes (Ti₃C₂T_x) combine high electrical conductivity, hydrophilicity, and abundance surface functional groups, which contribute to high energy density when compounded with carbon materials. In this work, carbon material derived from mineral water bottles is modified with cetyltrimethylammonium bromide (CTAB) that spontaneously forms into porous heterogeneous structures with Ti₃C₂T_x under electrostatic interactions. The carbon material hinders the reaggregation of Ti₃C₂T_x, while Ti₃C₂T_x increases the electrochemical activity on the surface of the carbon material. A hierarchical porous carbon with a large specific surface area of 1754.3 m² g⁻¹, promoting the electrolyte migration kinetics and high specific capacitance in 6 m KOH electrolyte (404.1 F g⁻¹ at 1 A g⁻¹). The symmetric SC made as‐prepared carbon electrode shows an extended voltage window (1.8 V), an optimal energy density (31.19 Wh kg⁻¹ at a power density of 450 W kg⁻¹) and a low capacitance decay (1% after 15 000 cycles) in 1.5 m Na₂SO₄. The preparation of electrode material with a unique structure provides a practical and innovative strategy for the value‐added utilization of waste plastics.